Some tools or elements in some machines are exposed to wear and must be periodically replaced. This is the case of paper machines used for manufacturing paper where a doctor with at least one blade that wears with use and must be periodically replaced is used.
Such machines have at least one roller from which the paper is generated, and the doctor can have different uses such as for cleaning the surface of the rollers or peeling the sheet of paper from the surface on which it adheres, for example. As mentioned, the doctor comprises at least one blade which acts on the roller by contact and which suffers wear, and further comprises a blade holder which supports the blade and allows assembling and removing same.
A way for detecting the wear of the blade before it becomes pernicious is by means of actual user experience, or even visually. These are not the most advisable techniques because the detection of the wear before it becomes pernicious is not assured in all cases (due to user oversight, for example) and also because it is not a comfortable and fast way for detecting same.
Other methods are also known where the wear of the blade is manually measured by means of devices that are suitable for such purpose in order to detect whether or not it is acceptable. For this purpose, the machine must be stopped periodically (periods which can depend on user experience or on previously established time, for example), accessing the blade with the relevant device and taking the measurement (there are cases in which it may even be necessary to completely or partially remove the blade from the doctor to take the measurement).
Document EP 1310592 A2 discloses measurement means for measuring the wear of the blade. The measurement can be taken contacting or without contacting the blade and in both cases a relative movement is required between the measurement means and the blade which allows measuring the wear of a blade when the blade is being changed, for example.
Document EP 1244850 A1 discloses a doctor in which the wear of the blade can be detected or measured during the operation thereof. The doctor comprises a blade, a support or blade holder which holds the blade and a main support which in turn holds the support, the support being able to rotate with respect to the main support. In one embodiment, the doctor comprises a sensor in the blade holder or in the main support for detecting the rotation or the movement between them, the wear of the blade being estimated depending on this detection. In another embodiment, the doctor comprises a plurality of optical fibers arranged in parallel in the blade, whereby light is passed there through such that, if a fiber is broken due to the wear of the blade, light no longer goes through the fiber and this event is detected, the wear thus being detected.